The PRESENT PERFECT is formed with the auxiliary verb " to have " in it's present tense form + the past participle of the main verb : go have/has gone play have /has played etc .... It is used to indicate an action that happened in an unspecified time in the past and could be still going in the present or terminated just now . You can't using when referring to a specified time in the past like yesterday or last year ( in that case you use the Past tense ), you rather use it with words like ' yet , just , never , already " for they don't specify a time in the past . - I think I have met her once before. - I have just finished my homework ( here the action is terminated in the present , but started at an unspecified time in the past ) ** Notice that when using this tense ,the action on a timeline can not exceed the present moment ! ( Thus used with 'just ' as well). The PRESENT PERFECT CONTINUOUS is formed as follows : The present perfect of the auxiliary verb 'to have ' + the main verb + ing Here it is like the present perfect about an action starting in an unspecified time in the past and extending possibly to the present moment ,yet the emphasis is on the process . The action here may have just finished ,but there is an interest in the present result . "He has been working all week long . ( Now he finished his work ,the result is him being very tired ) . The action could be also continuing in the present . She has being working on the project since 4 hours . ( She is still working on it ) . I hope it is a bit clear :)

The Present Perfect is used when an action happened at an unspecified time before now. The Present Perfect Continuous is used when an action happened in the past and has continued until now. I have studied German. (Present Perfect -- at some point before now I did the action of studying German but I am no longer doing that. ) I have been studying French since September. (Present Perfect Continuous -- I began my study of French in the past and I am still studying it today) These links might help: Present Perfect: http://www.englishpage.com/verbpage/presentperfect.html Present Perfect Continuous: http://www.englishpage.com/verbpage/presentperfectcontinuous.html